Add new port: libzvbi - VBI decoding library (teletext)

[Greisby]

Description

libzvbi (ZVBI) is a library for decoding VBI (Vertical Blanking Interval) data services, including:

• Teletext (ETS 300 706) — page-based text information broadcast in analogue and digital TV signals
• Closed captions (EIA 608) — North-American captioning standard
• VPS / WSS / XDS — programme identification and wide-screen signalling metadata

Why this port is needed

libzvbi is needed by FFmpeg to decode teletext pages from MPEG-2 Transport Streams (M2TS).
When FFmpeg is built with --enable-libzvbi, the libzvbi teletext decoder becomes available, enabling extraction of teletext subtitle pages from DVB broadcasts and recordings.

This is the standard approach used by broadcast and media-processing pipelines worldwide.
Without libzvbi, FFmpeg cannot decode teletext data embedded in DVB streams.

Build strategy

Platform	Build system	Notes
Windows	CMake	Custom CMakeLists.txt + MSVC-compat patch + pre-generated config.h/site_def.h
Linux/macOS	Autotools	Native ./configure via vcpkg_configure_make(AUTOCONFIG)

The upstream project uses autotools exclusively.
On Windows, a custom CMake build file is provided because autotools is impractical with MSVC.
The MSVC-compat patch (001-msvc-compat.patch) adds shim headers (unistd.h, strings.h, sys/) for POSIX APIs;
these shims are removed on non-Windows platforms before the autotools build runs.

Dependencies

Dependency	Condition	Purpose
libiconv	Always	Character set conversion (teletext)
pthreads	Windows	POSIX threading shim

Patches

Patch	Purpose
001-msvc-compat.patch	MSVC portability: adds POSIX shim headers + type aliases

---

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• The versioning scheme in vcpkg.json matches what upstream says.
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• Exactly one version is added in each modified versions file.

[dg0yt]

I don't want to review the CMakeLists.txt before it is accepted to vendor a CMake build system into the new port.

[dg0yt]

In general, we want:

• use the official build systems
• use the same build system for all targets
• use the latest maintainer function from port vcpkg-make instead of the legacy vcpkg_..._make functions.

[dg0yt]

Loosing the constructor property for other toolchains. Please adjust the patch to handle both implementations. (Hint: Put #if/else/endif in front of the line, define a macro to carry the attribute when applicable.)

[dg0yt]

gettext including autopoint would be available via dependencies.

So get rid of the misleading comment, and clarify what "true" means here:

Suggested change

	# autopoint (gettext) is not available in vcpkg's msys2 environment (Windows)
	# nor on the Android CI hosts; since NLS is disabled anyway, skip it.
	if(VCPKG_TARGET_IS_WINDOWS OR VCPKG_TARGET_IS_ANDROID)
	set(ENV{AUTOPOINT} true)
	endif()
	if(VCPKG_TARGET_IS_WINDOWS OR VCPKG_TARGET_IS_ANDROID)
	set(ENV{AUTOPOINT} true) # the program
	endif()

[dg0yt]

I don't like this pattern. Avoid the shims. Or put the shims in a subdir, and adjust the include path as needed. Or create them with portfile commands in the binary dirs, between configure and build.

[dg0yt]

There shouldn't be RPATH issues if upstream isn't doing crazy things.
If we don't want the tools, the port shouldn't build them.
Often it is just removing one SUBDIRS entry Makefile.am.

[Greisby]

Well, when I originally created this port, I ended up writing a CMake build for Windows because I couldn’t get it to build otherwise.

The Azure CI suggested a neat trick — set(ENV{AUTOPOINT} true) — but it still doesn’t build without autopoint.
So I eventually asked Copilot to generate a patch removing all references to autopoint so that reconfiguration would work.
If only I’d had Copilot back then!

Ok, now I'll examine your comments from yesterday and adjust accordingly.

[dg0yt]

The Azure CI suggested a neat trick — set(ENV{AUTOPOINT} true) — but it still doesn’t build without autopoint.
So I eventually asked Copilot to generate a patch removing all references to autopoint so that reconfiguration would work.
If only I’d had Copilot back then!

I assume I know where Copilot took the idea from.